Channel encoding/decoding is a relatively independent technology in a mobile communication system and is a key technology that decides performance of the mobile communication system. The purpose of channel encoding/decoding is to reduce the signal transmission power and overcome signal fading that is unavoidable in a radio transmission environment.
The combination of channel encoding/decoding and interleaving reduces the bit error rate. In comparison with non-encoding scenarios, the bit error rate of traditional convolutional codes can be reduced by two orders of magnitude to 1E−3-1E−4 and the bit error rate of Turbo (a computer software language) codes can be reduced to 1E−6. The Low Density Parity Check (LDPC) code is a new attraction in the channel encoding/decoding field and is widely used besides Turbo codes.
An important performance of channel encoding/decoding is the error correction capability (or protection capability) which is reflected by the number of packets that can be corrected within a total number of packets if a maximum of allowed lost packets is specified, or reflected by the percentage of packets that can be corrected when the number of lost packets exceeds the maximum of allowed lost packets. Generally, when other conditions are the same, the stronger the error correction capability of channel encoding/decoding is, the higher the redundancy rate of data codes will be.
To meet the requirements of higher data transmission speeds and more powerful error correction capabilities, High Speed Downlink Packet Access (HSDPA) which combines Adaptive Modulation and Coding (AMC), Hybrid Automatic Retransmission Request (HARQ), and fast NodeB scheduling, is adopted in the 3rd Generation (3G) Wideband Code Division Multiple Access (WCDMA) system to achieve high-speed downlink data transmission.
LDPC-based HARQ includes two categories: Chase and Incremental Redundancy (IR). Chase means that the previous transmitted packet is retransmitted in its entirety and that the receiver combines and decodes the early and later received information. IR means that redundancy bit information is added in retransmission and that the receiver combines and decodes the early and later received data blocks.
During the implementation of the present invention, the inventor, however, finds the prior art subject to at least the following problem: In order to support for IR, both coder and decoder are required to be of multi-rate capabilities, and result in more complex than Chase. However, if Chase is adopted, it will cause a low system throughput.